Spring Runoff Reality Check - May 7

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Peak runoff is past, and river discharges are declining quickly. Last weekend around Vail the Eagle River and Gore Creek were running high and turbid, although not really into flood stage, but throughout this last week they dropped and started clearing quickly. In the Colorado Rockies, snowpack in the Yampa-White catchment is now at 53% of average for 16 June; the upper Colorado River catchment is at 15%; the Gunnison catchment is at 4%, and the San Juan catchment is at 1%. So the snowpack is basically gone, and the hydrograph at the Cisco gauge has been steadily dropping since 10 June, indicating the peak of the runoff pulse passed that point a week ago. What this means is that the peak discharge for the year has already reached Lake Powell and inflows are all downhill from here, short of releases from water banked in reservoirs further upstream. If we look at those, in terms of major storage units Flaming Gorge on the Green is at 85%, Blue Mesa on the Gunnison at 67%, McPhee on the Dolores at 82%, and Navajo on the San Juan at 70%. So these reservoirs are not really brimming full, just adequate. Because they have their own local constituencies to serve, I would not look to major additional releases from those units going forward. The unusually hot June weather on the Western Slope of Colorado is also having an effect, in terms of direct sublimation of the very minor remaining snowpack above timberline, evapotranspiration by stressed vegetation, and vapor pressure deficit dynamics. Putting all this together, it would not surprise me if Lake Powell tops out for the year pretty close to the level of 3581 and change that BOR has predicted in their most recent 24-month June study, which will once again equate to less than 40% full. This will be enough to get kayaks through The Cut, but not necessarily much else for very long, since by August the lake level is predicted to be back down to 3577. So folks should get out there and take what they can get while they can get it. Then we go back to praying for a snow during the coming winter, which has now become a neurotic annual ritual in the Colorado River basin, where Lake Powell annually cycling around about 35% full seems to be the new normal.
 
The funny thing is we’ve already hit 3581’ with more to come before the end of June as the runoff winds down.

Every foot matters regarding how long the Cut stays open. It will certainly be open for the busy 4th of July holiday. So that’s a positive thing.

It will be interesting to see if the upcoming and unexpected rain event for Colorado can add a little extra juice down the home stretch heading into July. That would be helpful too…even if only temporary,
 
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Just figured id add this here. Some of it is open to interpretation as you wish as these are spitball numbers from the upper green river drainage on what I’m seeing now.

First off…fontenelle dam has slowly cranked up the release to 3600cfs which is up from the 1100cfs we saw for most of the spring (starting April 26th). I believe this lasts through the weekend. Obviously, all of this water directly feeds my home lake of Flaming Gorge. Fontenelle has jumped from around 33% full to about 85% full today. Inflows are dropping rapidly and it looks like while they ramp up releases the numbers will actually be in the red.

Flaming gorge is sitting at about 85% as well. Strange coincidence that’s where both these upper basin reservoirs are sitting? Or maybe they are trying to balance them the same way things are balanced other places. Regardless…it looks like this is where both reservoirs are going to top out at this year. In reading, flaming gorge plans to do their “smallmouth bass flow experiment” that you guys know all about, in the coming days. Looks like ramp up will begin June 24th and it will start ramping down on June 27th. I believe this “bump” wil make the flows go from about 950cfs to 4600cfs. So you guys will get a little reprieve from the falling lake Powell flows in a couple weeks. When every inch matters in the cut, I assume that’s newsworthy.

Im not good at finding much into the what releases they have planned for the rest of summer but that’s the short term outlook on what’s happening up here.
 
Please see attached, the rain forecast for next week or so within Upper Colorado Drainage Basin taken from Levi Cowen's most excellent tropical weather page. Note an average of 1.5-2.5 inches of moisture over most of basin. I have no idea how much this would translate to 'lake fill' but encouraging none-the-less.
 

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Yeah, note also the amount forecast for lower Colorado Basin (most of Arizona) that would help Mead et.al. Beware, however, that this forecast is for next 14 days (not a week or so) and is subject to change. Levi's website (Tropical Tidbits) shows two tropical storms hitting Mexico with abundant moisture circling north and historically, hurricanes/tropical storms that hit Mexico (on the gulf side) translate into potential moisture events for Southwest US. It could be interesting!
 
I flew from Denver to SLC today, and the Gore range and whatever the range is east of Aspen with Mount of the Holy Cross is brimming with snow still. I am staying positive!
 
dogslayer24 said:
Great post!
I do think the top out will be higher than 3581. We are already at 3580.5 as of this morning
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Based on where the lake level is today, we will clearly exceed the 3581.5 predicted by BOR in their June study 24-month study. But the hydrographs are falling fast now, so the peak lake level is not so far away, barring releases from Flaming Gorge or other upstream units. Also, because of the shape of the basin being filled, each additional foot of rise requires progressively more water to attain. And as past lake level graphs show, once we do hit the peak water level for the year we do not stay there for very long, since the current BOR release schedules from GCD call for progressively more water to be released downstream as we get deeper into summer. So folks who want to utilize The Cut should probably take that opportunity over the next 6 weeks or so. After that, no guarantees. As for the anomalous moisture coming up later this week from tropical storm remnants out of Texas, that will likely create mostly localized flash flood events for the next day or two, so it might be wise to avoid narrow side canyons, which may get scoured. This will also add to lake turbidity in areas beyond the main channel. As usual, June is proving to be a fairly dynamic month in the West as spring turns into summer.
 
PED said:
Please see attached, the rain forecast for next week or so within Upper Colorado Drainage Basin taken from Levi Cowen's most excellent tropical weather page. Note an average of 1.5-2.5 inches of moisture over most of basin. I have no idea how much this would translate to 'lake fill' but encouraging none-the-less.
Click to expand...
any moisture added it great because it slows down evaporation and transpiration from plants and soils which equates to runoff ...so bring them rains lol
 
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